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Structure. 2014 Oct 7;22(10):1489-500. doi: 10.1016/j.str.2014.07.014. Epub 2014 Sep 11.

A plug release mechanism for membrane permeation by MLKL.

Author information

1
Department of Biophysics, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA.
2
National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China.
3
Department of Biophysics, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA. Electronic address: jose@arnie.swmed.edu.

Abstract

MLKL is crucial for necroptosis, permeabilizing membranes through its N-terminal region upon phosphorylation of its kinase-like domain by RIP3. However, the mechanism underlying membrane permeabilization is unknown. The solution structure of the MLKL N-terminal region determined by nuclear magnetic resonance spectroscopy reveals a four-helix bundle with an additional helix at the top that is likely key for MLKL function, and a sixth, C-terminal helix that interacts with the top helix and with a poorly packed interface within the four-helix bundle. Fluorescence spectroscopy measurements indicate that much of the four-helix bundle inserts into membranes, but not the C-terminal helix. Moreover, we find that the four-helix bundle is sufficient to induce liposome leakage and that the C-terminal helix inhibits this activity. These results suggest that the four-helix bundle mediates membrane breakdown during necroptosis and that the sixth helix acts as a plug that prevents opening of the bundle and is released upon RIP3 phosphorylation.

PMID:
25220470
PMCID:
PMC4192069
DOI:
10.1016/j.str.2014.07.014
[Indexed for MEDLINE]
Free PMC Article

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